Saturday, September 27, 2008

History of Refludan

The name hirudin is derived from Hirudo medicinalis, the medicinal leech used since antiquity in the practice of blood-letting, or phlebotomy. As the leech fastens onto the patient's skin, its salivary glands secrete a powerful anticoagulant that prevents the blood clotting that would deprive the leech of its meal.

In 1884, John Haycraft, who was working in a pharmacology laboratory in Strasbourg, was able to demonstrate that leeches contained a substance with anticoagulant properties. Until the discovery of heparin, this substance was the only means physicians had to prevent blood from clotting.

Finally, in the late 1950s, attempts to isolate the anticoagulant agent in leech saliva were successful, and hirudin was named and classified as a thrombin inhibitor. In 1976, the primary chemical structure of hirudin was established. A number of difficulties arose, however, in isolating hirudin from medicinal leeches. A limited number of leeches was available due to the failure of breeding trials, and leeches were placed on the endangered species list.

Because of the shortage of leeches—and the potential value of hirudin for therapeutic purposes—hirudin was an appropriate candidate for production using genetic engineering. The development of recombinant technology has enabled production of large amounts or r-hirudin—now called lepirudin—which has many physicochemical characteristics and biochemical properties identical to those of the natural product.

Refludan injection contains the active ingredient lepirudin, which is a type of medicine called a hirudin. It is an anticoagulant medicine used to treat and prevent blood clots. Lepirudin is a synthetic version of the substance that leeches inject into flesh when biting to prevent blood clotting.

Blood clots normally only form to stop bleeding that has occurred as a result of injury to the tissues. Sometimes, however, a blood clot can form abnormally within the blood vessels. This is known as a thrombus. It can be dangerous because the clot may detach and travel in the bloodstream, where it becomes known as an embolus. The embolus may eventually get lodged in a blood vessel, thereby blocking the blood supply to a vital organ such as the heart, brain or lungs. This is known as a thromboembolism.

When blood begins to clot, a complicated cascade of chemicals is activated within the body. This results in the formation of a protein called thrombin. Thrombin is central to the complete process of blood clotting.

Lepirudin works by binding to thrombin and directly inhibiting its action, so interfering with the blood clotting.

Abnormal blood clots in the blood vessels are usually treated with an injectable anticoagulant medicine called heparin. Heparin is also used to prevent blood clots in people at risk, for example in people having orthopaedic surgery who are going to be immobile for a long period of time. However, in some people, heparin can cause the number of platelets in the blood to drop (a condition called heparin-associated thrombocytopenia). People who develop this condition cannot continue to have heparin treatment and lepirudin is used as an alternative.

Refludan is given as an injection or drip into a vein (intravenous infusion)

REFLUDAN is a bivalent direct thrombin inhibitor proven to significantly reduce the risk of serious consequences of heparin-induced thrombocytopenia (HIT). It is indicated for anticoagulation in patients with HIT and associated thromboembolic disease in order to prevent further thromboembolic complications.


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